The following account permissions are required by SQL Prompt:
For SQL Server 7 or SQL Server 2000, SQL Prompt requires administrative or dbo or Sys Admin permissions.
For SQL Server 2005 you can use the same permissions as for SQL Server 7/2000 or alternatively you can use the GRANT VIEW DEFINITION TO [{username}] which provides SQL Prompt with permission to retrieve the metadata without giving dbo access.
For SQL Server 2008 and SQL Server 2012, it may be necessary to grant VIEW SERVER STATE to access information about encryption keys otherwise a 'User does not have permission to perform this action' message may prevent the display of candidates.